Richard Edgeworth, the chief of Chicago’s aviation police, resigned from the Chicago Department of Aviation last week after being the subject of an investigation into why his officers couldn’t carry guns or respond to an active shooter.

In January, the union representing the city’s aviation police asked Mayor Rahm Emanuel to allow them to carry firearms on the job to increase security.

At the time, the union faulted Edgeworth for not shoring up security at O’Hare and Midway.